Schedule 2B 


August 16, 1921 


DEPARTMENT OF THE INTERIOR 

/ ALBERT B. FALL, Secretary 

( 0i BUREAU OF MINES 

n 

H. FOSTER BAIN, Director 


PROCEDURE FOR ESTABLISHING A LIST 
OF PERMISSIBLE ELECTRIC 

MOTORS 


FEES, CHARACTER OF TESTS, 
CONDITIONS UNDER WHICH 
TESTS AND INSPECTIONS WILL 
BE MADE 



WASHINGTON 

GOVERNMENT PRINTING OFFICE 
1S21 


Celected set 



The Bureau of Mines, in carrying out one of the provisions of its organic act—to 
disseminate information concerning investigations made—prints a limited free edition 
of each of its publications. 

When this edition is exhausted copies may be obtained at cost price only through 
the Superintendent of Documents, Government Printing Office) Washington, D. C. 

The Superintendent of Documents is not an official of the Bureau of Mines. His is an 
entirely separate office and he should be addressed: 

Superintendent of Documents, 

Government Printing Office, 

Washington , D. C. 

The general law under which publications are distributed prohibits the giving of 
more than one copy of a publication to one person. The price of this publication is 5 
cents. 


First edition September , 1918 r 


(2) 


LIBRARY OF CONGRESS 


RECEIVED 



&6byMENTS DIVISION 

nut .. .. 






T/v 1 £ ? 




/ 


PROCEDURE FOR ESTABLISHING A LIST OF PERMISSIBLE ELECTRIC MOTORS; FEES, 
CHARACTER OF TESTS, AND CONDITIONS UNDER WHICH TESTS AND INSPECTIONS 
WILL BE MADE. 


PRELIMINARY STATEMENT. 

AUTHORIZATION. 

An act of Congress (37 Stat., 681) approved February 25, 1913, 
contains the following provision in regard to tests or investigations 
performed by the Bureau of Mines: 

Tha t for tests or investigations authorized by the Secretary of the Interior under the 
provisions of this act, other than those performed for the Government of the United 
States or State Governments within the United States, a reasonable fee covering the 
necessary expenses shall be charged according to a schedule prepared by the Director 
of the Bureau of Mines and approved by the Secretary of the Interior, who shall 
prescribe rules and regulations under which such tests or investigations may be made* 
All moneys received from such sources shall be paid into the Treasury to the credit of 
miscellaneous receipts. 

The Bureau of Mines is prepared at its Pittsburgh Experiment 
Station to conduct tests of motors and their electrical accessories, 
such as are used in gaseous mines to operate conveyors, coal-cutting 
machines, electric drills, pumps, coal-loading apparatus, and similar 
equipment, for the purpose of determining the permissibility of such 
motors and their accessories and approving them as permissible for 
use in gaseous mines or dust-laden atmospheres. 

In the case of portable motors provided with trailing cables the term 
“ accessories’’ will mean all equipment and wiring up to and including 
the trailing cable, but will not include junction boxes or other fixed 
apparatus that may be used for connecting such trailing cables to the 
power supply. 

DEFINITIONS. 

Adequate .—The word “ adequate” means appropriate and sufficient 
as determined by mutual agreement of the manufacturers and the 
United States Bureau of Mines. 

Approved .—“ Approved'’ means accepted as suitable by the bureau. 

Normal operation .—“Normal operation’’ means the performance 
by each part of the equipment of those functions for which each part 
was designed. 

Permissible. —“Permissible” means approved by the bureau as 
permissible for use in gaseous mines or dust-laden atmospheres. 

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TESTS OF EQUIPMENTS FOR GASEOUS MINES. 

The conditions under which the Bureau of Mines will inspect and 
test motors and their electrical accessories to establish their permissi¬ 
bility for use in gaseous mines, are as follows: 

1. The tests will be made at the experiment station of the Bureau of 
Mines, at Pittsburgh, Pa. 

2. Applications for tests shall be addressed to the Director, Bureau 
of Mines, Washington, D. C., and shall be accompanied by a certified 
check or bank draft made pa}^able to the Secretary of the Interior, to 
cover the total fees required for the desired tests. 

A complete description, and a full set of the drawings shall be sent 
to the Electrical Engineer, Bureau of Mines, 4800 Forbes Street, 
Pittsburgh, Pa. 

The set of drawings shall include the following: 

A drawing or drawings clearly showing the character, size, and 
relative arrangement of the complete equipment used with the motor. 
The drawing or drawings shall specify the material of which all parts 
are made. 

A drawing or drawings showing in detail all parts of such motors 
and electrical accessories as might cause an ignition of gas. 

Any other drawings necessary to identify or explain any feature 
that is to be considered in the approval of the complete equipment. 

3. As soon as possible after receipt of his application for test, the 
manufacturer will be notified as to the date on which his equipment 
will be tested and the amount of accessory parts that it will be 
necessary for him to submit. 

4. The manufacturer shall deliver to the Bureau of Mines, 4800 
Forbes Street, Pittsburgh, Pa., two weeks prior to the date set for 
the test, the necessary parts for determining the permissibility of 
his equipment. The manufacturer shall provide a man to assist in 
the conduct of the tests and shall make preliminary preparations for 
conducting the tests, such as drilling and tapping the various accessory 
parts to accommodate the necessary pipe connections. The manu¬ 
facturer, if he so desires, may have a representative present through¬ 
out all the tests. 

5. No one is to be present during the permissibility tests except 
the necessary Government officers at the experiment station, their 
assistants, representatives of the manufacturer of the equipment 
under test, and such other persons as may be mutually agreed upon 
by the manufacturer and the bureau. 

6. Permissibility tests of motors and accessories will not be made 
unless motors and accessories have been completely developed and 
are m a form that can be put on the market. Permissibility tests 
will be made in the order of the receipt of application for them. 


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provided that the necessary equipment is submitted at the proper 
time. 

7. Development tests to assist the manufacturer in the design of 
equipment may be made at the request of the manufacturer and at 
the option of the bureau and will be charged for in amounts pro¬ 
portionate to the work involved. 

8. The details of the results of the tests shall be regarded as con¬ 
fidential by all present at the tests and shall not be made public 
in any way prior to the formal approval of the equipment by the 
Bureau of Mines. 

REQUIREMENTS FOR APPROVAL OF MOTORS AND THEIR 

ELECTRICAL ACCESSORIES. 

CLASSIFICATION OF PARTS. 

The various parts of motors and their electrical accessories that 
may cause ignition of gas shall be divided into four classes: 

Class 1 .—Class 1 shall include all parts, such as motors, controllers 
resistances, fuses, and switches, that, while in service in gaseous 
places, may produce sparks or flashes as the result of normal operation. 

Class 2 .—Class 2 shall include all parts, such as disconnecting 
switches, that may produce sparks or flashes as a result of normal 
operation, but need not be operated while the equipment is in a 
gaseous place. 

Class 3 .—Class 3 shall include all parts, such as wiring, that do 
not produce sparks or flashes as a result of normal operation, but 
may do so as a result of accident. 

Class 4 -—Class 4 shall include all mechanically held connections 
not inclosed in permissible compartments. 

GENERAL REQUIREMENTS PRESCRIBED FOR EACH CLASS. 

Class 1 .—All Class 1 parts shall be inclosed in permissible com¬ 
partments. 

Class 2 .—All Class 2 parts shall be completely inclosed in com¬ 
partments of adequate mechanical strength that are either permissible 
compartments or locked with an adequate lock. 

Class 3 .—All Class 3 parts shall be provided with adequate me¬ 
chanical protection of a strength and character proportionate to the 
risk of injury, or with permissible inclosures. 

Class 4 .—All Class 4 parts shall be designed with an adequate 
factor of safety to insure reliability. 

66348—21--2 




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GENERAL REQUIREMENTS FOR CONTROLLER AND PROTECTIVE 

APPLIANCES. 

Every motor shall be protected, together with its starting device, 
by adequate means for automatically opening the circuit. A switch 
or switches shall be arranged to entirely cut off the power supply 
from the motor. Automatic circuit interrupting devices shall be 
designed so that the device may be reset or renewed quickly and 
conveniently without meanwhile causing any of the permissible 
features of the equipment to be less effective. 

It is recognized that the necessary control and protective appli¬ 
ances will depend to a great extent upon the size and type of motor 
and the service for which the motor is intended and consequently 
the question of adequacy will need to be determined separately for 
each equipment. 

GENERAL REQUIREMENTS FOR CONDUCTORS AND WIRING. 

All wiring not inclosed in locked or permissible compartments 
shall have adequate mechanical and electrical protection. If flexi¬ 
ble metal conduit is used, special attention shall be given to the 
security of the fastenings at its end to make them adequate. 

GENERAL REQUIREMENTS FOR PORTABLE MOTORS. 

Portable motors shall be designed with extreme ruggedness; the 
auxiliary parts shall be mounted upon a common base with the 
motor as far as practicable, and with their frames electrically con¬ 
nected thereto. 

Cable reels used in connection with portable motors will be con¬ 
sidered as an accessory part of the equipment. 

Trailing cables used in connection with portable motors shall be 
adequate for the service they are required to perform. The trailing 
cables shall be attached to the frame of the apparatus or motor in 
such a manner as to eliminate injurious strains. The cable fasten¬ 
ings shall be so designed and arranged as to prevent short bends in 
the cable or mechanical injury to the insulation. The outer ends of 
trailing cables shall be provided with adequate means for attaching 
the cables to the power supply without personal hazard. 

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SPECIAL REQUIREMENTS FOR CLASS 1 PARTS. 

CONSTRUCTION. 

The construction of Class 1 parts must be especially durable. 
This requirement will be applied consistently to all the details of 
the parts under test in order that with proper care and maintenance 


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the permissible qualities of the part will remain unimpaired under 
the severe conditions imposed by mining service. 

Any protective devices used with such parts must not only be 
capable of preventing the passage of flames from the interior to the 
exterior of the casing, but must also possess sufficient mechanical 
strength to insure against the accidental destruction of their pro¬ 
tective qualities. If there are moving parts in connection with 
such devices, these parts should be so designed that there can be 
no interference with their movement. 

All leads entering permissible compartments shall pass through the 
casing by means of a properly protected insulated device of approved 
design. 

All joints in the casings of a permissible compartment must be 
metal-to-metal, so designed as to form a path not less than 1 inch 
long from the inside of the casing to the atmosphere. All bolt holes 
in casings must be bottomed or so arranged that the accidental omis¬ 
sion of a bolt will not give an opening through the casing. All open¬ 
ings in the casings of permissible compartments other than those 
provided with protective devices by the manufacturers must be 
tightly closed. It is desirable that such openings be as few as 
possible. 

CHARACTER OF TESTS. 

In testing Class 1 parts to establish their permissibility, the casings 
will be filled and surrounded with the most explosive mixture of 
Pittsburgh natural gas and air. The mixture within the casing will 
be ignited by a spark plug or other suitable means. 

Similar tests may also be made with greater and with less amounts 
of gas in the explosive mixture and with coal dust sifted into the 
casing or into the protective devices. Tests will be made to deter¬ 
mine the point of ignition that gives the greatest pressure. Not less 
than 10 tests will be made for each permissible compartment and 
more than that number if, in the opinion of the bureau’s engineers, 
more tests are necessary to prove the permissibility of the compart¬ 
ment under test. 

As a result of the permissibility tests of any compartment or com¬ 
partments, the internal explosion within the compartment or com¬ 
partments shall not ignite the gas surrounding the equipment nor 
discharge flames from any of the compartments. Neither shall there 
be developed dangerous afterburning 1 or excessive pressure in any 
of the compartments. 


i The term "afterburning” as used in this schedule is applied to the combustion, immediately after an 
explosion within a permissible compartment, of a gaseous mixture that was not within the casing at the 
time of the explosion, but was drawn in subsequently while the products of the explosion were cooling. 



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TESTS OF EQUIPMENT FOR DUST-LADEN ATMOSPHERES. 

The conditions under which the Bureau of Mines will inspect and 
test motors and electrical accessories to establish their permissi¬ 
bility for use in dust-laden atmospheres are as follows: 

1. The general requirements covering the place of tests, applica¬ 
tion, drawings, etc., will be the same as given for “ Tests of equip¬ 
ment for gaseous mines.” 

2. The same general classification of parts and similar require¬ 
ments for the several classes will be adhered to. 

3. In testing equipment designed for use in coal mines, it will be 
assumed that an equipment which passes when tested in percentages 
of methane and of methane and coal dust, as outlined under u Tests 
of equipment for gaseous mines ,’’ will meet the requirements for dust¬ 
laden atmospheres. 

4. For equipments approved for service in or about pulverized coal 
plants, in addition to the tests usually made for equipments used in 
gaseous mines, special attention will be given to the method used to 
prevent short circuits between electrical parts due to accumulation of 
coal dust and additional tests will be made to determine whether the 
equipment will keep dust from entering the interior of the compart¬ 
ments in dangerous amounts. 

5. For equipments used in or about aluminum or other industrial 
plants, having or likely to have dust-laden atmospheres, the bureau 
reserves the right to devise special tests best adapted to prove the 
safety of equipment for each special service. In some cases it will 
probably require a research by the bureau to determine the proper 
test procedure. 

SPECIAL REQUIREMENTS FOR COMPLETE EQUIPMENTS. 

Equipments, including permissible motors and their electrical 
accessories, will not be considered as permissible for use under any 
of the following conditions: 

If used without the approval plate mentioned hereafter. 

If used with openings in any of the permissible compartments 
other than those openings provided with protective devices by the 
manufacturer. This condition refers to all openings but especially 
to those closed by removable covers during normal operation. 

If the equipment when in operation is not complete with all of the 
parts considered in its approval. 

APPROVAL-PLATE REQUIREMENTS. 

The manufacturer shall be required to attach to the equipment 
an approval plate bearing the seal of the Department of the Interior, 
Bureau of Mines, and an appropriate caution statement. 






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Ihe size, material, and design of the approval plate shall be 
subject to the approval of the bureau. The manufacturer will be 
furnished a photographic print of the wording and seal to be incorpo¬ 
rated in the approval plate design. 

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NOTIFICATION OF MANUFACTURER. 

As soon as the bureau s engineers are satisfied that an equipment 
is permissible for use in gaseous mines or in dust-laden atmospheres, 
the manufacturer shall be notified to that effect. 

As soon as the manufacturer receives formal notification that his 
equipment met the requirements prescribed by the bureau, he shall 
be free to advertise such equipment as permissible. 

DRAWINGS OF APPROVED EQUIPMENTS TO BE FILED. 

As the safety of a permissible motor or its accessories depends 
largely on its construction, the approval of an equipment must 
identify the details of construction on which the approval is based. 
This identification will be accomplished by reference to a list of 
drawings and photographs that show in detail such parts as directly 
or indirectly affect the safety of the motor or any of its accessories. 
Each list of drawings will be given a number to facilitate reference. 
A copy of each drawing will be hied with the Bureau of Mines. 

SCOPE OF APPROVAL. 

The bureau’s approval of any equipment shall be construed as 
applying onjy to equipment of the specific type, class, form, and 
rating that have the same construction in the details directly or 
indirectly affecting the safety of the equipment as the one inspected, 
tested, and approved for permissibility by the bureau. 

Manufacturers shall, before claiming the bureau’s approval for any 
further modification of an approved equipment, submit to the 
bureau drawings that shall show the extent and nature of such 
modifications in order that the bureau may decide whether test of 
the remodeled part will be necessary for approval. 

WITHDRAWAL OF APPROVAL. 

The bureau reserves the right to rescind for cause, at any time, 
any approval granted under the conditions herein set forth. 


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FEES FOR TESTING MOTORS AND THEIR ACCESSORIES. 

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The following fees, to be charged on and after the date of approval 
of this schedule, have been established and approved by the Secretary 
of the Interior: 


ITEM 1—SEGREGATED CHARGES FOR PERMISSIBILITY TESTS. 


The following charges will be made for tests made separately or 
repeated during the course of an investigation: 


Complete preliminary inspection. 

Tests to prove the permissibility of parts under (’lass 1: 

Each motor. 

Each controller... 

Each resistance. 

Fuses and switches. 

Tests and inspections necessary to prove the adequacy of parts 

3, and 4. 

Complete final inspection. 


. $10.00 

. 37.50 

. '37.50 

. 37.50 

. 37.50 

under Classes 2, 

. $10.00-30.00 

. 10.00 


ITEM 2.-CHARGES FOR DEVELOPMENT TESTS. 


Special tests to assist the manufacturer in the development of 
equipment will be charged for in accordance with the work involved. 
Each request for special tests should be accompanied by a fee of 
$100 made payable to the Secretary of the Interior. Any unused 
moneys from such deposits will be refunded at the completion of the 
special tests on request by the manufacturer. 

SYNOPSIS OF PROCEDURE TO BE FOLLOWED IN MAKING APPLI¬ 
CATION FOR TESTS, SUBMITTING MATERIAL, CONDUCTING 

TESTS, AND NOTIFYING APPLICANT OF RESULTS. 

1. Application for tests should be addressed to the Director of the 
Bureau of Mines, Washington, D. *C. This application should be 
accompanied by check or draft made payable to the Secretary of the 
Interior. Duplicate copies of the application and a set of drawings 
should be sent to the Electrical Engineer, Bureau of Mines, 4800 
Forbes Street, Pittsburgh, Pa. 

2. As soon as the application has been reviewed by the bureau’s 
engineers the applicant will be notified of the date of tests. 

3. After the applicant has received this notification he should send 
the material required to the Electrical Engineer, 4800 Forbes Street, 
Pittsburgh, Pa. The material should be delivered not less than two 
weeks in advance of the date set for the beginning of the tests. 

4. The tests will be begun on the date set and continued until the 
equipment has been approved, rejected, or withdrawn. 









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5. After the bureau’s engineers have considered the results of the 
tests, a formal report of the approval or disapproval of the equipment 
will be made to the applicant in writing by the Director of the Bureau 
of Mines. No verbal report will be made, and the details of the tests 
must be regarded as confidential by all present. 

The rules and regulations, including fees, set forth in this schedule 
shall be immediately effective upon the approval of the schedule and 
shall take the place of previous regulations published under Schedule 
2-A. 

Id. Foster Bain, 

Director. 


Approved August 16, 1921. 

E. C. Finney, 

First Assistant Secretary. 



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